ASTM D3336-20b

Standard Test Method for Life of Lubricating Greases in Ball Bearings at Elevated Temperatures

SIGNIFICANCE AND USE
4.1 This test method can be used to evaluate the ability of grease to provide adequate lubrication for extended periods of ball bearings operating under light loads at high speeds and elevated temperatures.
SCOPE
1.1 This test method covers the evaluation of the performance of lubricating greases in ball bearings operating under light loads at high speeds and elevated temperatures.  
1.2 The values stated in SI units are to be regarded as standard.  
1.2.1 Exception—The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific warning statements, see 8.1.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Oct-2020
• ICS: 75.100 - Lubricants, industrial oils and related products
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.G0.05 - Functional Tests - Temperature

Relations

• Refers: ASTM A600-92a(2024) - Standard Specification for Tool Steel High Speed
• Effective Date: 01-Mar-2024
• Refers: ASTM A600-92a(2016) - Standard Specification for Tool Steel High Speed
• Effective Date: 01-Mar-2016
• Refers: ASTM A600-92a(2010) - Standard Specification for Tool Steel High Speed
• Effective Date: 01-Oct-2010
• Refers: ASTM A600-92a(2004) - Standard Specification for Tool Steel High Speed
• Effective Date: 01-Sep-2004
• Refers: ASTM A600-92a(1999) - Standard Specification for Tool Steel High Speed
• Effective Date: 10-Sep-1999

Overview

ASTM D3336-20b: Standard Test Method for Life of Lubricating Greases in Ball Bearings at Elevated Temperatures is a key international standard published by ASTM International. This test method outlines a procedure for evaluating the performance and extended life of lubricating greases in ball bearings operating under light loads, high speeds, and elevated temperatures. The method is applicable to industries seeking reliable data for grease selection in critical machinery where long-term lubrication and resistance to thermal stress are required.

This standard is widely referenced in the lubrication, manufacturing, and maintenance sectors, ensuring product quality and safety while meeting international testing and reporting criteria.

Key Topics

• Performance Evaluation: Describes how to evaluate lubricating greases for their ability to maintain effective lubrication and protect bearings when subjected to light loads, high rotational speeds, and elevated operational temperatures.
• Test Parameters: Specifies testing conditions such as the type of ball bearing (typically SAE No. 204 size), operational speeds up to 10,000 r/min, temperatures up to 371°C (700°F), and load requirements.
• Grease Failure Criteria: Outlines indicators of lubricant failure, including excessive increases in spindle input power, abnormal temperature rises, and mechanical issues such as bearing loading or drive belt slippage.
• Statistical Data and Precision: Asserts the importance of replication and statistical analysis, recognizing the Weibull distribution of grease life results rather than a simple normal distribution.
• Safety and Compliance: Stresses the necessity for users to establish appropriate safety, health, and environmental practices during testing, and to comply with applicable regulations.

Applications

ASTM D3336-20b is applied across various sectors where high-performance lubrication is critical, including:

• Automotive Industry: Assessment of lubricating greases used in high-speed automotive wheel bearings and electrical motor applications.
• Aerospace Sector: Evaluation of greases intended for aircraft bearings, which require exceptional longevity and performance at elevated temperatures.
• Industrial Machinery: Selection and testing of grease formulations for high-speed production equipment, especially where unplanned downtime due to lubrication failure can be costly.
• Research and Development: Used by lubricant and bearing manufacturers to benchmark new product formulations and ensure compliance with industry standards.
• Quality Assurance and Supplier Validation: Provides an objective and repeatable method for comparing lubricant performance between suppliers and during production quality checks.

Related Standards

Organizations often use ASTM D3336-20b alongside related standards to ensure comprehensive bearing and lubricant evaluation:

• ASTM A600: Specification for Tool Steel High Speed, relevant for the construction of test bearings utilized in high-temperature testing.
• ABMA Standard 4: Defines tolerance and gauging practices for ball and roller bearings, pertinent to the measurement and characterization of test components.
• ISO 6204: Pertains to bearing sizes and specifications used for laboratory testing.
• Other ASTM Grease and Lubricant Standards: Provides complementary procedures for characterizing lubricating properties, such as thermal stability, corrosion resistance, and water washout.

Keywords: ball bearing, lubricating grease, grease life, elevated temperature, ASTM D3336-20b, grease performance testing, performance evaluation, bearing lubrication standard.

By following ASTM D3336-20b, organizations can ensure the reliability, safety, and performance of lubricating greases for demanding ball bearing applications, supporting robust maintenance practices and the development of higher-performing lubrication products.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D3336 − 20b
Standard Test Method for
Life of Lubricating Greases in Ball Bearings at Elevated
Temperatures
This standard is issued under the fixed designation D3336; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* 3. Summary of Test Method
1.1 This test method covers the evaluation of the perfor- 3.1 A grease lubricated SAE No. 204 size ball bearing is
mance of lubricating greases in ball bearings operating under rotated at 10 000 r/min under light load at a specified elevated
light loads at high speeds and elevated temperatures. temperature. Tests are continued until failure or completion of
a specified number of hours of running time.
1.2 The values stated in SI units are to be regarded as
standard.
4. Significance and Use
1.2.1 Exception—The values given in parentheses are math-
4.1 This test method can be used to evaluate the ability of
ematical conversions to inch-pound units that are provided for
grease to provide adequate lubrication for extended periods of
information only and are not considered standard.
ball bearings operating under light loads at high speeds and
1.3 This standard does not purport to address all of the
elevated temperatures.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 4,5
5. Apparatus
priate safety, health, and environmental practices and deter-
5.1 Test Spindle (see Figs. 1-4), capable of operating at
mine the applicability of regulatory limitations prior to use.
speeds of 10 000 r⁄min and temperatures as high as 371 °C
For specific warning statements, see 8.1.
(700 °F).The test bearing seat dimension shall be 19.99 mm to
1.4 This international standard was developed in accor-
20.00 mm (0.7870 in. to 0.7874 in.). For spindles having the
dance with internationally recognized principles on standard-
test bearing and the support bearing in the same housing (CRC
ization established in the Decision on Principles for the
Type, Fig. 1, Fig. 2, and Fig. 4) the internal construction of the
Development of International Standards, Guides and Recom-
spindle shall be such that the outboard support bearing, or both
mendations issued by the World Trade Organization Technical
bearings are free to float axially in the housing. In designs
Barriers to Trade (TBT) Committee.
where both bearings are free to float, the spindle shaft shall
havea0.508 mmto0.762 mm(0.020 in.to0.030 in.)freeaxial
2. Referenced Documents
movement or end play. The outboard bearing seat dimension
2.1 ASTM Standards:
should be 19.99 mm to 20.00 mm (0.7870 in. to 0.7874 in.).
A600 Specification for Tool Steel High Speed
5.1.1 The test unit design should be such that a finger spring
2.2 ABMA Standard: washer(Fig.1)andaZ-Springwasher(Fig.2)producesa22 N
Standard 4, Tolerance Definitions and Gaging Practices for
to 67 N (5 lbf to 15 lbf) thrust load on the floating outboard
7,5
Ball and Roller Bearings support bearing.
5.2 Bearing Housing:
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Complete apparatus is available from Falex Corp., 1020 Airpark Dr., Sugar
Subcommittee D02.G0.05 on Functional Tests - Temperature. Grove, IL 60554.
Current edition approved Nov. 1, 2020. Published November 2020. Originally If you are aware of alternative suppliers, please provide this information to
approved in 1975. Last previous edition approved in 2020 as D3336 – 20a. DOI: ASTM International Headquarters. Your comments will receive careful consider-
10.1520/D3336-20B. ation at a meeting of the responsible technical committee, which you may attend.
2 6
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Pope Machinery Corporation GreaseTest Spindles No. P-1911 or P-6301A-HT
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM (Fig. 1) and No. P-7605-B (Fig. 2); and Falex Corp. spindles of the type shown in
Standards volume information, refer to the standard’s Document Summary page on Fig. 1 and Fig. 3 have been found satisfactory for this purpose.
the ASTM website. The sole source of supply of the apparatus known to the committee at this time
Available fromAmerican Bearing ManufacturersAssoc., 2025 M St., NW, Ste is Falex Part No. 643-187-070, Falex Corp. 1020 Airpark Dr., Sugar Grove, IL
800, Washington, DC 20036. 60554.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3336 − 20b
FIG. 1 Test Spindle (Both Bearings Floating)
FIG. 2 Test Spindle (Test Bearing Held)
tions L-35-54 and CRC L-35-62).
5.2.1 For CRC Type Spindles—The bearing housing diam-
eter shall be 47.005 mm to 47.021 mm (1.8506 in. to
5.2.2 For Navy Type Spindles (Test Bearing Mounted Out-
1.8512 in.)togiveproperbearingmounting.Constructionshall
side Spindle Housing)—The bearing housing shall be con-
be such that the test bearing is equipped with flush spacers or
structed of material similar to that of the test bearing and shall
shields to confine the grease to the bearing. The spacers or
be tempered to retain dimensional stability at temperatures up
shields shall have a clearance between the inside diameter and
to 371 °C (700 °F). Internal diameter shall be 47.005 mm to
the shaft of 0.127 mm to 0.178 mm (0.005 in. to 0.007 in.) per
47.021 mm (1.8506 in. to 1.8512 in.). The housing cover shall
side.
be flush fitting to confine the grease to the bearing. Provision
shall be made for insertion in the housing of one or two small
NOTE 1—This type of spindle is described in CRC Research Technique
thermocouples which shall lightly press on and be in continual
for the Determination of Performance Characteristics of Lubricating
Grease in Antifriction Bearings at Elevated Temperature (CRC Designa- contact with the outer race of the test bearing. The housing
D3336 − 20b
FIG. 3 Test Spindle (with Radial Load)
FIG. 4 Test Spindle Thrust Load Design
shall be fitted with lugs to accommodate a yoke and added 5.5 Control Equipment:
weight so that a radial load may be applied to the test bearing.
5.5.1 The temperature at the outside diameter of the test
Athrust load of 22 N 6 2 N (5 lbf 6 0.55 lbf) shall be applied
bearing shall be maintained within 3 °C (5 °F) of the specified
to the outer race of the bearing by means of a helical spring
test temperature. The temperature control equipment shall be
calibrated at room temperature.
adequate to maintain the temperature at the outer race of the
test bearing within the limits specified by control of the oven
5.3 Motor Drive Assembly—Spindle bracket and constant
belt tension motor drive assembly capable of providing spindle temperature. The oven temperature shall be controlled by
speeds up to 10 000 r⁄min 6 200 r⁄min by means of an endless means of a thermocouple placed in the oven cavity.
belt. The motor shall be mounted so that a belt tension of
5.5.2 Suitable equipment such as adjustable reset relay and
approximately 67 N (15 lbf) can be maintained on the test
overload device for shutting off oven heaters and drive motor
spindle pulley.
and other accessory equipment (timer, recorder, etc.) shall be
5.4 Oven, removable, capable of producing a test tempera- provided. Oven temperature as well as bearing temperature
ture of 371 °C (700 °F) within 1 ⁄2 h. should be recorded.
D3336 − 20b
6. Materials can also be measured by volume and applied to the bearing by
means of a syringe. The grease shall be worked uniformly into
6.1 Test Bearing, General Requirements—ISO 6204 (SAE
both sides of the bearings, using a narrow blade spatula,
No. 204) size, manufactured to ABEC-3 quality. See Annex
makingsurethatthegreasedoesnotextendbeyondthefacetof
A1, which describes ABMA’s standard method of measuring
the races. For CRC Type spindles the support bearing shall be
radial internal clearances of ball bearings. Support bearings of
packed full.
CRC Type spindles shall be identical to the test bearings.
6.1.1 Lower Temperature Bearing—For testing at tempera- 8.3 Assemblethetestbearing,supportbearing,andZ-spring
tures of 149 °C (300 °F) and below, a size 6204 bearing (PCN (see Fig. 1 and Fig. 2) on the spindle and fix the thermocouples
12-433360-12) has been found satisfactory. This bearing is into position so that it is in contact with the outer race of the
fabricated from AISI 52100 steel, with a retainer fabricated test bearing (CRC Type spindles). For tests at 232 °C (450 °F)
fromAISI C1010 steel and with an internal clearance range of and above, replace the finger spring washer for each test. For
0.021 mm to 0.028 mm (0.0008 in. to 0.0011 in.). Navy Type spindles insert the test bearing into the housing and
6.1.2 Higher Temperature Bearing—For testing at tempera- pressthebearingontothespindlebyapplicationofalightforce
tures above 149 °C (300 °F), the bearing shall be fabricated on the inner race. Place the cover plate in position, fix the
from heat-resistant steel and equipped with a ball retainer thermocouples into position, and apply the radial and thrust
fabricated from suitable material, both capable of withstanding loads.
temperatures as high as 371 °C (700 °F). Bearings fabricated
from18-4-1highspeedorM-50(SpecificationA600)toolsteel 9. Procedure
with retainers fabricated from heat-treated silver-plated beryl-
9.1 Rotate the bearing by hand for approximately 100
liumcopper havebeenfoundsatisfactoryforthispurpose.The
revolutions in each direction at a speed not exceeding
bearing shall have a radial clearance of from 0.025 mm to
200 r⁄min. Start the drive motor and heater simultaneously and
0.031 mm (0.0010 in. to 0.0012 in.).
adjust the temperature controller to raise the bearing to test
temperature within 1 ⁄2 h. After 2 h of test operation at spee
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D3336 − 20a D3336 − 20b
Standard Test Method for
Life of Lubricating Greases in Ball Bearings at Elevated
Temperatures
This standard is issued under the fixed designation D3336; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This test method covers the evaluation of the performance of lubricating greases in ball bearings operating under light loads
at high speeds and elevated temperatures.
1.2 The values stated in SI units are to be regarded as standard.
1.2.1 Exception—The values given in parentheses are mathematical conversions to inch-pound units that are provided for
information only and are not considered standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. For specific warning statements, see 8.1.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
A600 Specification for Tool Steel High Speed
2.2 ABMA Standard:
Standard 4, Tolerance Definitions and Gaging Practices for Ball and Roller Bearings
3. Summary of Test Method
3.1 A grease lubricated SAE No. 204 size ball bearing is rotated at 10 000 r/min under light load at a specified elevated
temperature. Tests are continued until failure or completion of a specified number of hours of running time.
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.G0.05 on Functional Tests - Temperature.
Current edition approved July 1, 2020Nov. 1, 2020. Published July 2020November 2020. Originally approved in 1975. Last previous edition approved in 2020 as
D3336 – 20.D3336 – 20a. DOI: 10.1520/D3336-20A.10.1520/D3336-20B.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American Bearing Manufacturers Assoc., 2025 M St., NW, Ste 800, Washington, DC 20036.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3336 − 20b
FIG. 1 Test Spindle (Both Bearings Floating)
4. Significance and Use
4.1 This test method can be used to evaluate the ability of grease to provide adequate lubrication for extended periods of ball
bearings operating under light loads at high speeds and elevated temperatures.
4,5
5. Apparatus
5.1 Test Spindle (see Figs. 1-4), capable of operating at speeds of 10 000 r ⁄min and temperatures as high as 371 °C (700 °F). The
test bearing seat dimension shall be 19.99 mm to 20.00 mm (0.7870 in. to 0.7874 in.). For spindles having the test bearing and the
support bearing in the same housing (CRC Type, Figs. 1-3Fig. 1, Fig. 2, and Fig. 4) the internal construction of the spindle shall
be such that the outboard support bearing, or both bearings are free to float axially in the housing. In designs where both bearings
are free to float, the spindle shaft shall have a 0.508 mm to 0.762 mm (0.020 in. to 0.030 in.) free axial movement or end play. The
outboard bearing seat dimension should be 19.99 mm to 20.00 mm (0.7870 in. to 0.7874 in.).
5.1.1 The test unit design should be such that a finger spring washer (Fig. 1) and Fig. 2) should be sucha Z-Spring washer (Fig.
7,5
2 that a finger spring washer ) produces a 22 N to 67 N (5 lbf to 15 lbf) thrust load on the floating outboard support bearing.
5.2 Bearing Housing:
5.2.1 For CRC Type Spindles—The bearing housing diameter shall be 47.005 mm to 47.021 mm (1.8506 in. to 1.8512 in.) to give
proper bearing mounting. Construction shall be such that the test bearing is equipped with flush spacers or shields to confine the
grease to the bearing. The spacers or shields shall have a clearance between the inside diameter and the shaft of 0.127 mm to
0.178 mm (0.005 in. to 0.007 in.) per side.
NOTE 1—This type of spindle is described in CRC Research Technique for the Determination of Performance Characteristics of Lubricating Grease in
Antifriction Bearings at Elevated Temperature (CRC Designations L-35-54 and CRC L-35-62).
5.2.2 For Navy Type Spindles (Test Bearing Mounted Outside Spindle Housing)—The bearing housing shall be constructed of
material similar to that of the test bearing and shall be tempered to retain dimensional stability at temperatures up to 371 °C
(700 °F). Internal diameter shall be 47.005 mm to 47.021 mm (1.8506 in. to 1.8512 in.). The housing cover shall be flush fitting
to confine the grease to the bearing. Provision shall be made for insertion in the housing of one or two small thermocouples which
Complete apparatus is available from Falex Corp., 1020 Airpark Dr., Sugar Grove, IL 60554.
If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a
meeting of the responsible technical committee, which you may attend.
Pope Machinery Corporation Grease Test Spindles No. P-1911 or P-6301A-HT (Fig. 1) and No. P-7605-B (Fig. 2); and Falex Corp. spindles of the type shown in Fig.
1 and Fig. 23 have been found satisfactory for this purpose.
The sole source of supply of the apparatus known to the committee at this time is Falex Part No. 643-187-070, Falex Corp. 1020 Airpark Dr., Sugar Grove, IL 60554.
D3336 − 20b
FIG. 2 Test Spindle (Test Bearing Held)
FIG. 3 Test Spindle (with Radial Load)
shall lightly press on and be in continual contact with the outer race of the test bearing. The housing shall be fitted with lugs to
accommodate a yoke and added weight so that a radial load may be applied to the test bearing. A thrust load of 22 N 6 2 N (5 lbf
6 0.55 lbf) shall be applied to the outer race of the bearing by means of a helical spring calibrated at room temperature.
5.3 Motor Drive Assembly—Spindle bracket and constant belt tension motor drive assembly capable of providing spindle speeds
up to 10 000 r ⁄min 6 200 r ⁄min by means of an endless belt. The motor shall be mounted so that a belt tension of approximately
67 N (15 lbf) can be maintained on the test spindle pulley.
D3336 − 20b
FIG. 4 Test Spindle Thrust Load Design
5.4 Oven, removable, capable of producing a test temperature of 371 °C (700 °F) within 1 ⁄2 h.
5.5 Control Equipment:
5.5.1 The temperature at the outside diameter of the test bearing shall be maintained within 3 °C (5 °F) of the specified test
temperature. The temperature control equipment shall be adequate to maintain the temperature at the outer race of the test bearing
within the limits specified by control of the oven temperature. The oven temperature shall be controlled by means of a
thermocouple placed in the oven cavity.
5.5.2 Suitable equipment such as adjustable reset relay and overload device for shutting off oven heaters and drive motor and other
accessory equipment (timer, recorder, etc.) shall be provided. Oven temperature as well as bearing temperature should be recorded.
6. Materials
6.1 Test Bearing, General Requirements—ISO 6204 (SAE No. 204) size, manufactured to ABEC-3 quality. See Annex A1, which
describes ABMA’s standard method of measuring radial internal clearances of ball bearings. Support bearings of CRC Type
spindles shall be identical to the test bearings.
6.1.1 Lower Temperature Bearing—For testing at temperatures of 149 °C (300 °F) and below, a size 6204 bearing (PCN
12-433360-12) has been found satisfactory. This bearing is fabricated from AISI 52100 steel, with a retainer fabricated from AISI
C1010 steel and with an internal clearance range of 0.021 mm to 0.028 mm (0.0008 in. to 0.0011 in.).
6.1.2 Higher Temperature Bearing—For testing at temperatures above 149 °C (300 °F), the bearing shall be fabricated from
heat-resistant steel and equipped with a ball retainer fabricated from suitable material, both capable of withstanding temperatures
as high as 371 °C (700 °F). Bearings fabricated from 18-4-1 high speed or M-50 (Specification A600) tool steel with retainers
fabricated from heat-treated silver-plated beryllium copper have been found satisfactory for this purpose. The bearing shall have
a radial clearance of from 0.025 mm to 0.031 mm (0.0010 in. to 0.0012 in.).
6.2 ASTM n-Heptane.
6.3 Mineral Spirits, reagent grade.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1272. Contact ASTM Customer
Service at [e-mail].
The sole source of supply of the apparatus known to the committee at this time is Bearing MRC204S17, SKF Bearings, www.skf.com. If you are aware of alternative
suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical
committee, which you may attend.
Described in 1996 Annual Book of ASTM Standards, Vol 05.04, Annex 2, Section A2.7 on Reference Materials.
D3336 − 20b
7. Test Conditions
7.1 Temperature—As specified up to 371 °C (700 °F).
7.2 Speed—10 000 r ⁄min 6 200 r ⁄min.
7.3 Test Cycle:
7.3.1 Twenty-one and one-half hours running at temperatures of 149 °C (300 °F) and below—2 ⁄2 h shutdown without applied
heat. Shutdown refers to the shutdown of both the spindle motor drive and oven.
7.3.2 Twenty hours running at temperatures of above 149 °C (300 °F)—
...